JP2500527B2 - Defrost control method for air conditioner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting control system for an air conditioner in which frost adhering to an outdoor heat exchanger during heating operation is removed by a heat refrigerant flowing through the outdoor heat exchanger. It is about.

[0002]

2. Description of the Related Art FIG. 7 is a refrigerant circuit diagram showing a conventional air conditioner described in, for example, Japanese Patent Publication No. 1-20709. In the figure, (1) is a compressor, (2) is an accumulator, (3) is a four-way valve, (4) is an outdoor heat exchanger, (5) is an expansion device, (6) is an indoor heat exchanger, (7) is an outdoor unit blower fan, and (8) is an indoor unit blower fan. These are compressor (1) -four-way valve (3)
-Outdoor heat exchanger (4) -Expansion device (5) -Indoor heat exchanger
(6) -Four-way valve (3) -The accumulator (2) and the refrigerant pipe are sequentially connected in an annular shape, and during the cooling operation, the high temperature and high pressure refrigerant gas from the compressor (1) is exposed to the outside as shown by the solid arrow. It is sent to the heat exchanger (4), where it radiates heat and condenses, and then evaporates and absorbs heat in the indoor heat exchanger (6) through the expansion device (5) to cool the room, and during heating operation, the broken line As shown by the arrow, the high-temperature and high-pressure refrigerant gas from the compressor (1) is reversely circulated and is sent to the indoor heat exchanger (6), where heat is dissipated for heating.

Generally, in an air conditioner having a refrigeration cycle of this kind, when defrosting is performed during heating operation, the four-way valve (3) is switched to switch the heating cycle to a cooling cycle and the blower fans (7) (8) are stopped. By doing so, the high-temperature and high-pressure refrigerant gas is caused to flow to the outdoor heat exchanger (4) to remove the frost adhering to it. Further, a method has also been proposed in which the refrigerant circuit to the indoor heat exchanger (6) is bypassed during defrosting, and the refrigerant gas is directly supplied from the compressor (1) to the outdoor heat exchanger (4).

[0004]

However, in the conventional defrosting method for an air conditioner, a great amount of time is required for defrosting, and the heating operation cannot be performed during that time, which causes a decrease in room temperature and impairs comfort. There was a point.

The present invention has been made to solve the above problems, and an object thereof is to obtain a defrosting method for an air conditioner capable of defrosting in a short time.

[0006]

A control system for an air conditioner according to a first aspect of the present invention is a speed detecting means for detecting the speed of an induction motor for driving a compressor, and a detected speed from the speed detecting means. Signal, the speed command signal, the defrosting timing detection signal of the air conditioner to calculate the required slip of the induction motor to output a slip command signal to the slip calculation means and the slip command signal from the slip calculation means Providing a speed control means for controlling the speed of the induction motor so as to make the slip corresponding to the slip calculation means, by applying the defrosting timing detection signal, outputs a signal instructing a larger slip than when the signal is not applied. It is configured to do.

A control system for an air conditioner according to a second aspect of the present invention is a power factor detecting means for detecting the power factor of an induction motor for driving a compressor, instead of the speed detecting means in the first aspect. The slip calculation means is adapted to calculate the required verification of the induction motor from the power factor signal from the power factor detection means, the speed command signal, and the defrosting timing detection signal of the air conditioner. It is a thing.

[0008]

In the control system of the air conditioner according to the first and second aspects of the present invention, since the induction motor for driving the compressor is operated more smoothly than during normal operation during defrosting operation,
This motor is operated at high rotation speed, high power factor, low dynamic rate and high input power, and the refrigerant gas discharged from the compressor becomes superheated and becomes hotter and is sent to the outdoor heat exchanger for defrosting time. Is greatly shortened.

[0009]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention, in which (1) is a compressor, (2) is an accumulator,
(3) is a four-way valve, (4) is an outdoor heat exchanger, (5) is an expansion device,
(6) is an indoor heat exchanger, (7) is a blower fan for outdoor units, (8)
Is an indoor unit blower fan, and the above is the same as the conventional example shown in FIG. (9) is an induction motor that drives the compressor (1), (10) is an inverter that supplies three-phase AC power of variable frequency to the induction motor (9), (11) is an inverter (10), a blower fan (7 ) (8) and a control circuit for controlling the four-way valve (3), etc., (12)
Is an outdoor unit pipe temperature sensor that detects the pipe temperature of the outdoor heat exchanger (4) and inputs the detected temperature signal from the outdoor unit pipe temperature sensor to the control circuit (11) as a defrosting timing detection signal. Reference numeral (13) is a speed sensor for detecting the speed of the induction motor (9) and inputting a speed signal to the control circuit (11).

FIG. 2 is a block diagram showing the details of the inverter (10) and the control circuit (11) in FIG.
(10a) is a converter circuit, (10b) is a smoothing capacitor, (10a)
c) is an inverter circuit, (10d) is a DC current detector, (14) is an AC power supply, (15) is a waveform shaping circuit that shapes the signal from the speed sensor (13), and (16) is a waveform shaping circuit ( Speed signal fr indicating the instantaneous rotation speed of the induction motor (9) output from 15)
And a slip control circuit that calculates the slip frequency command signal fs * from the reference frequency command fo * and the defrosting timing detection signal from the outdoor unit piping temperature sensor (12), and (17) responds to the slip frequency command fs * accordingly. Speed-voltage conversion circuit that calculates and outputs the voltage command signal V *, (18) is a speed-voltage conversion circuit
It is a base amplifier circuit that amplifies the voltage command signal V * output from (17) and supplies it to the inverter circuit (10c).

The speed sensor (13) and the waveform shaping circuit (15)
And the speed control means, the slip control circuit (16) constitutes the slip calculation means, and the speed-voltage conversion circuit (17), the base amplifier circuit (18) and the inverter circuit (10c) constitute the speed control means, respectively. are doing.

Next, the operation of this embodiment will be described with reference to FIGS. Figure 3 shows the operating characteristics of the induction motor (9).
FIG. 4 is a flowchart showing the flow of the defrosting operation operation. In Fig. 3, the horizontal axis is the slip (%) of the induction motor (9).
(19) is the input power (W) to the induction motor (9), (20)
Is the input current (A), (21) is the efficiency (%) of the induction motor (9),
(22) shows the change characteristics of the torque (N · m) of the induction motor (9) and (23) shows the change characteristics of the power factor (%) of the induction motor (9) with respect to slip. Note that the cooling and heating operation of the refrigerant circuit in FIG. 1 is exactly the same as that in the case of FIG. 7, so description thereof will be omitted.

First, during the heating operation of the air conditioner, after the compressor operating cumulative time of 50 minutes has elapsed in step (24) of FIG. 4,
When the outdoor unit piping temperature sensor (12) detects a temperature of −5 ° C. or lower in step (25), the defrosting timing detection signal is input to the control circuit (11) and the process proceeds to step (26), where the four-way valve (3 ) Is switched to the cooling operation side (solid line arrow in Fig. 1), and step (27)
The outdoor unit blower fan (7) stops. Next step (2
When the compressor (1), that is, the induction motor (9) reaches the maximum operating frequency in 8), the process proceeds to step (29), and the waveform detected by the speed sensor (13) in the slip control circuit (16) of the control circuit (11) is detected. From the speed signal fr shaped by the shaping circuit (15), the defrosting timing detection signal and the reference frequency command fo *,
A slip frequency command signal fs * of a large slip that causes the induction motor (9) to operate at high power factor and low efficiency is arithmetically output, and a voltage command signal V * corresponding thereto is output from the speed-voltage conversion circuit (17). It is output, and the induction motor is output via the base amplifier circuit (18) and the inverter circuit (10c) according to this voltage command.
(9) is controlled.

Then, the slip of the induction motor (9) increases, the operating point of the induction motor (9) shifts from A to B, and the input increases. As a result, the input power is poured into the compressor (1) without increasing the work rate, and the temperature of the compressor (1) rises without increasing the pressure of the discharged refrigerant. Then, the compressor (1) functions as a heater, the increased input to it becomes almost the heating amount of the refrigerant, and the frost adhering to the outdoor heat exchanger (4) is rapidly removed. If 10 minutes or more have passed since the defrosting started (step (30)) or the outdoor unit piping temperature rises to 8 ° C or higher (step (31)), the outdoor unit is used in steps (32) and (33). The blower fan (7) is restarted and the four-way valve (3) is on the heating side.
(Fig. 1 dashed arrow), the defrosting operation ends and the heating operation is restarted.

Example 2. 5 and 6 show another embodiment of the present invention, FIG. 5 is a block diagram showing the details of the inverter (10) and the control circuit (11), and FIG. 6 is a flow chart showing the flow of the defrosting operation. , In the figure, (9) ~ (12), (14)
And (18) are the same as in Fig. 2, and (34) is an induction motor.
(9) Three-phase current transformer for power factor detection, (35) obtains and outputs a power factor signal Pr corresponding to the instantaneous power factor of the induction motor (9) by the current signal from the current transformer (34) An instantaneous power factor detection circuit (36) calculates a slip frequency (frequency slipped from the synchronous frequency) corresponding to this as shown in FIG. 3 from the power factor signal Pr from the instantaneous power factor detection circuit (35). The slip frequency calculation circuit that outputs the slip frequency signal fr, (37) is the slip frequency signal fr output from the slip frequency calculation circuit (36), the reference frequency command fo *, and the removal from the outdoor unit piping temperature sensor (12). Slip frequency command signal fs * from frost timing detection signal
The frequency control circuit for calculating (38) is the slip frequency command f
It is a frequency-voltage conversion circuit that calculates and outputs a voltage command signal V * according to it from s *. The same steps as those in FIG. 4 of FIG. 6 are designated by the same reference numerals.

The three-phase current transformer (34) and the instantaneous power factor detection circuit
(35) and the power factor detection means by slip frequency calculation circuit (3
6) and the frequency control circuit (37), the slip calculation means,
And frequency-voltage conversion circuit (38), base amplifier circuit
The speed control means is constituted by the (18) and the inverter circuit (10c).

Next, the operation of this embodiment will be described with reference to FIG. Since steps (24) to (28) are the same as those in FIG. 4, their description will be omitted. When the compressor (1) reaches the maximum operating frequency in step (28), the process proceeds to step (39), where the instantaneous power factor detection circuit (35) detects the instantaneous current of the induction motor (9) from the current signal from the current transformer (34). The power factor signal Pr corresponding to the power factor is obtained, and the process proceeds to step (29). In the slip frequency calculation circuit (36), the power factor signal Pr from the instantaneous power factor detection circuit (35) is used as shown in FIG.
The slip frequency signal fr corresponding to this is calculated, and the frequency control circuit (37) calculates the slip frequency signal fr from the slip frequency calculation circuit (36) and the defrosting timing detection signal and the reference frequency command fo *. From the above, a slip frequency command signal fs * of a large slip such that the induction motor (9) is operated at high power factor and low efficiency is arithmetically output, and the voltage command signal V * corresponding thereto is output from the frequency-voltage conversion circuit (38 ), And the base amplifier circuit (1
8), the induction motor (9) is controlled via the inverter circuit (10c). The subsequent operation is similar to that of the embodiment shown in FIG.

In the above embodiment, only the so-called reverse system in which the refrigerant circuit is switched from the heating operation to the cooling operation at the time of defrosting has been described, but another defrosting method, for example, to the indoor heat exchanger at the time of defrosting is performed. A so-called hot gas bypass system in which the refrigerant gas is bypassed and the refrigerant gas is allowed to flow directly from the compressor to the outdoor heat exchanger, and the same effect as that of the above-described embodiment is obtained.

[0019]

As described above, according to the first aspect of the present invention, the speed detecting means for detecting the speed of the induction motor for driving the compressor, the detected speed signal from the speed detecting means,
A slip calculation means for calculating the required slip of the induction motor from the speed command signal and the defrosting timing detection signal of the air conditioner and outputting a slip command signal, and a slip corresponding to the slip command signal from the slip calculation means. A speed control means for controlling the speed of the induction motor is provided so that the slip computing means outputs a signal for instructing a larger slip by applying the defrosting timing detection signal than when the signal is not applied. Therefore, the refrigerant flow rate is secured and the refrigerant temperature rises during defrosting, the defrosting time is shortened, and there is an effect that a defrosting control method for an air conditioner that does not impair comfort is obtained. .

According to a second aspect of the present invention, instead of the speed detecting means in the first aspect, a power factor detecting means for detecting the power factor of the induction motor for driving the compressor is provided, and the slip Since the calculation means calculates the required verification of the induction motor from the power factor signal from the power factor detection means, the speed command signal, and the defrost timing detection signal of the air conditioner, It has the same effect as that of the first aspect of the invention.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a first invention of the present invention.

FIG. 2 is a block diagram showing details of an inverter and a control circuit in FIG.

FIG. 3 is an operation characteristic diagram of the induction motor of this embodiment.

FIG. 4 is a flowchart showing the flow of defrosting operation of this embodiment.

FIG. 5 is a block diagram showing details of an inverter and a control circuit in an embodiment of the second invention of the present invention.

FIG. 6 is a flowchart showing the flow of a defrosting operation operation of this embodiment.

FIG. 7 is a refrigerant circuit diagram showing a conventional air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 4 Outdoor heat exchanger 6 Indoor heat exchanger 9 Induction motor 10c Speed control means (inverter circuit) 13 Speed detection means (speed sensor) 15 Speed detection means (waveform shaping circuit) 16 Slip calculation means (slip control) Circuit 17 Speed control means (speed-voltage conversion circuit) 18 Speed control means (base amplifier circuit) 34 Power factor detection means (three-phase current transformer) 35 Power factor detection means (instantaneous power factor detection circuit) 36 Slip calculation means (Slip frequency calculation circuit) 37 Slip calculation means (frequency control circuit) 38 Speed control means (frequency-voltage conversion circuit)

Claims (2)

(57) [Claims] 1. When the air conditioner equipped with a compressor driven by an induction motor driven by AC power, an indoor heat exchanger, and an outdoor heat exchanger is in heating operation, the outdoor heat exchanger is used. In the defrosting control system of the air conditioner configured to remove the adhered frost by the heat refrigerant flowing through the outdoor heat exchanger, the speed detection means for detecting the speed of the induction motor, and the detection from the speed detection means. A slip command signal for calculating a required slip of the induction motor from the speed signal, the speed command signal, and the defrosting timing detection signal of the air conditioner, and outputting a slip command signal, and a slip command signal from the slip calculator. A speed control means for controlling the speed of the induction motor is provided so that the slip corresponds to, and the slip calculating means is provided by applying the defrosting timing detection signal when the signal is not applied. A defrosting control method for an air conditioner, which is configured to output a signal instructing a larger slip. 2. The outdoor heat exchanger is operated during heating operation of an air conditioner including a compressor driven by an induction motor energized by AC power, an indoor heat exchanger and an outdoor heat exchanger. In a defrosting control system for an air conditioner, which removes adhered frost by a heat refrigerant flowing through the outdoor heat exchanger, a power factor detecting means for detecting the power factor of the induction motor, and the power factor detecting means. From the detected power factor signal from, the speed command signal, and the defrosting timing detection signal of the air conditioner from the slip calculation means and the slip calculation means for calculating the required slip of the induction motor and outputting the slip command signal Is provided with speed control means for controlling the speed of the induction motor so that the slip will be in accordance with the slip command signal, and the slip calculating means is provided when the defrosting timing detection signal is applied and the signal is not applied. A defrosting control method for an air conditioner, which is configured to output a signal instructing a larger slip.